One address, and a real person reads it.
To make a report easy to act on, it helps to send:
Both calculators are checked against the arithmetic they claim to do, including the rounding, so please include the exact numbers if you think a figure is wrong — a worked example is far quicker to investigate than a description of one.
Please do not send anything sensitive. The calculators never need your account details, card numbers or receipts, and neither do we.